A digital light processing (DLP) projection apparatus includes an illumination system, a digital micro-mirror device (DMD) and a projection lens. The illumination system is used to provide an illumination beam, the digital micro-mirror device is used to convert the illumination beam into an image beam, and the projection lens is used to project the image beam onto a screen to form an image on the screen. Ultra-high pressure mercury lamp is the light source used in early illumination system, and the ultra-high pressure mercury lamp can provide white light as an illumination beam. With the development of illumination technology, some light sources such as the light emitting diode light source and laser light source with power-saving advantage are gradually being used.
FIG. 1 is a schematic view of a conventional illumination system using a laser light source. As shown in FIG. 1, in the conventional illumination system 100, the blue beam 112 provided by the laser light source module 110 sequentially passes through the collimating element 122, the dichroic mirror 130 and the lenses 123 and 124 and is irradiated to the rotatable phosphor wheel 140. The phosphor wheel 140 can be divided into a green phosphor zone, a yellow phosphor zone and a light penetration zone. The back surface 141 of the phosphor wheel 140 corresponding to the green phosphor zone and the yellow phosphor zone is disposed with a reflective element (not shown). The blue beam 112 is sequentially irradiated to the green phosphor zone, the yellow phosphor zone and the light penetration zone. When the blue beam 112 is irradiated to the green phosphor zone and the yellow phosphor zone, the green beam 113 and the yellow beam 114 are excited. The reflective element reflects the green beam 113 and the yellow beam 114 to the dichroic mirror 130. The green beam 113 and the yellow beam 114 are reflected by the dichroic mirror 130, pass through the lens 123 and are irradiated to the rotatable filter wheel 150. In addition, a portion of the blue beam 112 passes through the light penetration zone and is irradiated to the filter wheel 150 sequentially via the lenses 126 and 127, the reflective elements 161 and 162, the lens 128, the reflective element 163, the lens 129 and the dichroic mirror 130.
The filter wheel 150 has a red filter zone and a transparent zone corresponding to the yellow phosphor zone, a green filter zone corresponding to the green phosphor zone, and a diffusion zone corresponding to the light penetration zone. The green beam 113 is irradiated to the green filter zone, the yellow beam 114 is irradiated to the red filter zone and the transparent zone, and the blue beam 112 is irradiated to the diffusion zone by controlling the filter wheel 150 and the phosphor wheel 140 to rotate with each other. As a result, the beam entering the light integration rod 170 after passing through the filter wheel 150 includes a blue beam, a green beam and a red beam for forming a color image and a yellow beam for increasing the luminance.
Since the structure of the conventional illumination system 100 is complicated and many optical elements are required, the conventional illumination system 100 has some disadvantages such as high cost, large volume and poor optical efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.